I) Field of the Invention
The present invention relates to ventilation systems and to the form and configuration of breathing tubes therefor.
II) Summary of the Prior Art
Administration of gases to patients from a ventilator via one or more breathing tubes is well known in the art. In particular it is well known to provide a pair of breathing tubes, being an inhalation and an exhalation tube which connects to a yoke connector at the patient. Furthermore it is known to provide a humidification device in the inhalation line, usually close to the ventilator, to provide the inhaled gases at elevated humidity levels.
These systems have the disadvantage that the pair of breathing tubes are bulky and inconvenient to work with.
More recently breathing tubes have been suggested in which the inhalation line is concentrically located within a larger tube, with the space between the inhalation tube and the larger tube forming the exhalation path. These are said to improve upon the earlier dual tube configuration by reducing the bulk and inconvenience and by providing counterflow heat exchange between the inhalation and exhalation gases. Examples of such circuits are shown in U.S. Pat. No. 3,865,106, U.S. Pat. No. 4,007,737, U.S. Pat. No. 4,462,397, U.S. Pat. No. 4,463,755, U.S. Pat. No. 4,637,384, U.S. Pat. No. 4,967,744 and U.S. Pat. No. 5,404,873.
These configurations have encountered problems with humidified gases as condensation forms on the inside of the wall of the outer tube (which wall is in contact on its outer side with the ambient air) and collects along the lower side of the tube. This poses a particular problem as the inner inhalation tube also tends to lie along the lower side of the larger exhalation tube and therefore in contact with the collected condensate. This has an adverse affect on the maintenance of the temperature of the inhalation gases in the inhalation tube. While some of the gases in the inhalation tube remain at appropriate temperatures, those adjacent the lower wall of the inhalation tube can become subject to significant temperature drop and subsequent condensation onto the tube or wall. It will be readily appreciated that formation of condensation makes it both difficult to control the operation of the humidifier to maintain comfortable levels of humidity at the patient and also can require the incorporation of devices which allow the egress of the condensation and ensure that such liquid does not reach the patient.
It is therefore an object of the present invention to provide a ventilation system and/or a breathing tube therefor which at least goes some way to overcoming the above disadvantages or which will at least provide the healthcare industry with a useful choice.
In a first aspect the invention consists in a humidified gases ventilation system comprising:
a patient interface means for connection with a patient and immediate delivery of gases thereto,
a humidified ventilation means for providing a flow of pressurised and humidified gases, and
a gases pathway connecting between said patient interface means and said humidified ventilation means and having an internal conduit and a surrounding conduit within which said internal conduit is disposed, said space between said internal conduit and said surrounding conduit connected with the inhalation port of said humidified ventilation means for supply of said humidified gases therethrough to said patient interface means.
In a still further aspect the invention consists in a breathing tube for a humidified gases ventilation system comprising:
an internal conduit,
a surrounding conduit within which said internal conduit is disposed, and
a connector at one end of said internal conduit and said surrounding conduit, said connector having an inhalation gases port for connection to the inhalation gases supply port of a ventilator, and a gases flow path from said inhalation gases port to said space between said internal conduit and said surrounding conduit.
To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.